Question

QUESTION 15 Which of the following are TRUE? Select All That Apply Trisomy only occurs to chromosome 13 (Patau syndrome), chromosome 18 (Edward syndrome) and 21 (Down syndrome) since we have never seen individuals with trisomy in other chromosomes Poly-X syndrome is caused by non-disjunction, but Turner syndrome is caused by some othre factors In order for Jacob syndrome to happen, non-disjunction should happen during meiosis II and male X-linked genes affect female, but not male In pedigree analysis, if neither of parents shows the trait but some of their kids show the trait, this trait is recessively inherited trait

Answer 1

Statement 2,3 and 5 are TRUE.

Polysomy is a condition in which either the mother egg cell or the father sperm cell divides incorrectly,resulting in an extra X chromosome in the child.This random error is called Non-disjunction,Whereas turner syndrome is due to chromosomal abnormality in which all or part of the X chromosomes is missing or altered.While most peoples have 46 chromosomes,people with turner syndrome only have 45 chromosomes.

The incidence of XYY chromosome remain undiagonised because of their normal apperance and fertility,and the absence of severe symptoms.The extra Y chromosome is usually a result of nondisjunction during paternal meosis II,ie in males.Males with XYY syndrome have 47 chromosomes because of the extra Y chromosomes.This condition is called jacobs syndrome,XYY karyotype or YY syndrome.

In first generation ,neither parents have a trait,but their kids have.This condition is called recessive trait.Because there are unaffected parents that have affected offspring,so it can be assumed that the trait is recessive.And the trait affect males more than females is the trait is X linked.

1 and 4 are FALSE.

Because trisomy is a type of polysomy in which there are three instances of a particular chromosome,instead of the normal two.But it can occur with any chromosome of the 23 pairs,not only in 13,18 and 21.Trisomy 16 is one of the most common trisomy in human pregnancies.Also trisomy 9,trisomy 8 all exists.

X linked genes exclusively affects males more than females,because males have only one X chromosome,mutations in an X linked gene would not be masked by a normal allele and thus would manifest in males.